This application incorporates by reference Taiwanese application Serial No. 89119776, filed Aug. 23, 2001.
1. Field of the Invention
The invention relates in general to a technique of extraction to obtain the product with high concentration and high recovery yield, and more particularly to the extracting glycosides from a herb using an aqueous two-phase system.
2. Description of the Related Art
With the rapid development of biotechnology, the techniques of separating and extracting biologically important compounds from animal and plant sources have become an area of great importance. The problems of traditional separation technologies include low recovering yields, and, especially, low yield resulting from fermentation of the solution due to the long period of extraction. These problems hinder the development of medication to a certain extent. The traditional process of separation and purification depend on the chemical and physical properties of materials and products, however, the method mainly applied is that of chromatography. There are several drawbacks to the use of traditional solvents and chromatography including:
1. The process of extraction is time-consuming.
2. Solvents such as dichloromethane or chloroform applied in the process of extraction are toxic and hazardous to human, as well as cause serious environmental pollution.
3. The cost of the process is high.
4. Undesired chemical reactions occur during purification.
The objective of this invention, therefore, is to develop a method of phase separation using an aqueous two-phase system to obtain the product with high concentration and high recovery yield, which possess advantages such as simple procedures and equipments, low-cost production, and partial recycling and reuse of materials used in the process.
According to the objective of present invention, a process for the extraction of glycosides from herb described as follows:
(a) A herb is ground and mixed with water and then agitated. After filtration, the first filtrate is collected in a beaker while the residue is removed and mixed with water and filtered again. An aqueous extractive solution is made up of the first and the second crude extracts.
(b) The aqueous extractive solution is concentrated to about 1-10% of solid content.
(c) 5 wt %xcx9c30 wt % of salt, 5 wt %xcx9c30 wt % of polyol and 0 wt %xcx9c30 wt % of alcohol are added to the concentrated solution and mixed thoroughly. Phase separation is then carried out at a temperature between 4xc2x0 C. to 90xc2x0 C., after which the aqueous layer is separated from the polyol layer. The preferred temperature is in the range of room temperature to 70xc2x0 C.
(d) The aqueous layer is removed from the two-phase system, and concentrated in vacuo to give a solid which is dried.
(e) The resulting solids in step (d) is then suspended with a solvent to a concentration of 60%xcx9c99%, and then sonicated. The first filtrate and residue are then obtained after centrifugation and filtration.
(f) Repeat step (e) at least once, to obtain the second filtrate and residue.
(g) The first and second filtrates are combined and concentrated in vacuo to give the final solid product rich in glycosides.
According to the objective of present invention, another process for the extraction of glycosides from herb is further provided. Steps (a)xcx9c(f) are the same as the process abovementioned. After step (f), the first and second filtrates are combined and sitting on the bench for about 12xcx9c18 hours at a temperature between xe2x88x92110xc2x0 C. to 15xc2x0 C., which the preferred temperature is in the range of xe2x88x9210xc2x0 C. to 10xc2x0 C., and the depositions are removed by means of filtration to obtain a final filtrate. Then, the final filtrate is concentrated in vacuo to give the final solid product rich in glycosides.
The invention achieves the extraction of glycosides from a herb by providing a new aqueous two-phase system separation method that includes an aqueous extractive solution, 5 wt %xcx9c30 wt % of salt, 5 wt %xcx9c30 wt % of polyol, and selectively 0 wt %xcx9c30 wt % of alcohol. The salts can be dihydrogen phosphate, hydrogen phosphate, phosphate, or a mixture thereof; it also can be sulfates, chlorides, oxalates, or acetates.